10 of them.
Meter
As you haven't given a unit of 0.89, it makes the most sense if we call this metres. So a metre has 100cm. If we convert them in order to metres we get: 0.89, 0.88, 0.9, 0.87 all of metres. So 9 tenths of a metre is the longest
There are 9 tenths in 9 tenths.
9dm is 9 decimeters or nine tenths of a meter. It is less than a meter, so it is smaller than 6 meters.
3.5 of a meter
4.5 meters = 45 tenths of a meter
Ten of them.
9/10 of 3 = 2.7
It is: 9/10 or 0.9
40 cm
Ten.